Brucella species are facultative intracellular, non-encapsulated, non-motile, and gram-negative coccobacilli, which are transmitted by the consumption of unpasteurized milk and dairy products or by direct contact with infected animals (1). Brucellosis still remains as a major health problem causing a high degree of morbidity and economic loss in many regions, particularly in the Mediterranean, Middle East, and Latin America, but it is rare in Korea (2). However, recently, the incidence rate of Brucellosis is on the rise in Korea (3). Although brucellosis affects any organs, including the musculoskeletal and reticuloendothelial systems, osteoarticular diseases, including sacroiliitis, peripheral arthritis, spondylitis, osteomyelitis, and bursitis are the most common complication (4). We describe a case of brucellar spondylitis as the cause of non-specific back pain, with a review of MRI findings.

A 59-year-old male cattle farmer was presented with increasing lower back pain, which steadily developed over 2 months. His pain was unresponsive to rest and pain killers and it was worse at night. Additionally, he complained of fever and night sweating. He had no medical history of any diseases, including hypertension, diabetes, tuberculosis or hepatitis.

On physical examination, his body temperature was 37.8℃. His lower back movement was significantly painful in all directions, and tenderness was present on the lumbar vertebral region. No neurologic abnormality was detected. Laboratory findings on the peripheral blood test showed a raised erythrocyte sedimentation rate (ESR) and C-reactive protein to 80 mm/h and 2.64 mg/dL, respectively. However, no abnormality was reported in other peripheral blood and biochemical tests, and blood culture was negative. On detailed questioning, he had a history of contact with a Brucella-infected cow. Brucellar standard tube-agglutination test, which measures serum immunoglobulin G levels against Brucellar antigen, was measured at 1 : 320, and the patients was diagnosed with brucellar infection.

The lumbar spine MRI was performed with a 1.5-T Gyroscan ACS-NT system (Philips Medical Systems, Best, the Netherlands) using a spine coil. Axial and sagittal T1 and T2 weighted images and short-tau inversion recovery were obtained via MRI scanners. Also, T1 axial and sagittal contrast enhanced images were obtained. Lumbosacral spine MRI showed low signal intensity in L2 and L3 vertebral bodies on T1 weighted image and heterogeneous high signal intensity on T2 weighted image (Fig. 1A, B). In contrast, patchy heterogeneous irregular enhancement was detected in the affected L2 and L3 vertebral bodies. Disc space narrowing was not definitely detected, but minimal endplate involvement was seen in the anterior portion of L2 and L3 vertebral bodies. Also, irregular heterogeneous enhancement of paraspinal soft tissue was seen (Fig. 1C, D). All MR images are compatible with spondylitis in L2 and L3 vertebral bodies.

The patient was started on combination of oral rifampin, streptomycin, and doxycycline. The patient's back pain subsided during the course of medical treatment.

Brucella species are small gram-negative and aerobic coccobacilli that are transmitted most commonly through the ingestion of unpasteurized milk products or by direct contact with infected animals (1-3). Species that cause human brucellosis are Brucella melitensis, B. abortus, B. suis, and B. canis. B. abortus is detected mostly in Korea (3). The symptoms of brucellosis are non-specific, including fever, headache, back pain, myalgia, fatigue, sweating, anxiety or depression, and hepatobiliary or gastrointestinal abnormalities (5). The non-specific and commonly subtle nature of the symptoms results in difficulty of establishing an early diagnosis. In a patient suspected of having brucellosis, a detailed history taking of direct contact with infected animals or consumption of their products is important for early diagnosis and treatment (1, 3). In our case, confirming the patient's vocation and history on recent contract of brucellosis infected cow enabled us to make early diagnosis and to initiate the treatment. Brucellosis may affect various body organs, and spondylitis is the most prevalent and important complication of brucellosis in adults with frequency ranging from 2% to 50% (6). The lumbar region is the most frequent site of occurrence, whereas the cervical region is the least affected site of brucellar spondylitis (5).

Definite diagnosis of brucellosis is established by clinical manifestations and the isolation of brucella species from blood or bone marrow cultures (1, 2). In the absence of bacteriologic confirmation, a positive serology for brucella (titer over 1 : 160 in a standard tube agglutinin test or a 4-fold rise in brucella-antibody titer in the interval of 2 weeks) is considered definite diagnosis (2). Particularly in Korea, because tuberculosis is an endemic disease, tuberculous or brucella infections of the spine can be confusing. Both are caused by intracellular pathogens, which are difficult to isolate or identify in a short period (4). Although ESR is not a useful indicator for the diagnosis of brucellar spondylitis, elevated ESR has been observed in a majority of case reports, which may be used as valuable parameter for monitoring response to therapy (1).

MRI is the most preferred method of choice for the diagnosis of brucellar spondylitis, because it provides better demonstration of marrow change and paravertebral soft tissue spreading than other imaging techniques (7). MRI is very useful in differentiating brucellar spondylitis from tumor or degeneration, but radiographically, differentiation between tuberculous and brucellar spondylitis is complicated (8). There are only few reports on differential MRI findings between tuberculous and pyogenic spondylitis (5, 7, 8).

Lumbar spine, especially lower, is common site for pyogenic spondylitis. Brucellar spondylitis has more intact vertebral structure, more frequent disc association, diffuse vertebral osteomyelitis, less soft tissue involvement around the paraspinal area and absent gibbus deformity than other pyogenic or tuberculous spondylitis (9). In contrast, tuberculous spondylitis usually manifests on MRI with thinly and smoothly enhanced abscess wall and abnormal paraspinal signal with good demarcation (8). Also, tuberculous spondylitis has more frequent findings of subligamentous spread that spans 3 or more vertebrae and more narrowing of disc space than spondylitis due to brucella or other pyogenic causes. Paraspinal mass in tuberculous spondylitis is usually larger than that of brucellar spondylitis (7, 10). Another reported characteristic of tuberculous spondylitis includes frequent involvement of the posterior vertebral bodies and arches (8).

Yet, there has been a standard treatment regimen for the brucellosis, and it is treated with mixed combinations of antibiotics. The most effective treatment is known to be SDR combination (Streptomycin, Doxycycline, and Rifampin), and this combination is found to reduce failure and relapse (10).

In conclusion, due to rarity of the disease and non-specific nature of its symptoms and signs, brucellar spondylitis requires more attention from physicians to make early diagnosis. For patients with unknown fever, consumption of unpasteurized milk, and occupations that have a risk of contracting the infection, a physician must question possibility of brucellosis, and it must be included for differential diagnosis. It is also considered that MRI is an imaging modality that offers higher possibility of making the diagnosis. Thus, its use and careful interpretation of MRI is essential in making early diagnosis of brucellar spondylitis to initiate treatment.